JP3650921B2 - Dilution gas flow controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dilution gas flow control device used for quantitative analysis of PM (Particulate Matter, particulate matter such as soot) contained in a gas discharged from an automobile diesel engine or the like.
[0002]
[Prior art]
One of the methods for measuring PM in the exhaust gas is in accordance with the filter weight method. In this type of measuring device, in order to collect PM contained in sample gas branched and sampled from a tunnel for diluting the sample gas, in order to collect PM in the exhaust gas in a steady state where the engine speed is constant A dilution gas flow control device is provided in parallel with the sample gas flow path provided with the filter, and provided with a bypass flow path for flowing exhaust gas in an unsteady state where the engine speed is unstable.
[0003]
FIG. 4 schematically shows a configuration of a conventional dilution gas flow rate control apparatus. In this figure, 1 is a diesel engine mounted on an automobile, for example, and 2 is an exhaust pipe connected thereto. 3 is inserted and connected to the exhaust pipe 2, the probe for sampling exhaust gas G flowing in the exhaust pipe 2, the downstream side is connected to the dilution tunnel 4 for diluting the San flop rings are exhaust gas G. Reference numeral 5 denotes a dilution air supply pipe connected to the upstream side of the dilution tunnel 4.
[0004]
6 is a gas flow path connected to the downstream side of the dilution tunnel 4 and through which the diluted exhaust gas (hereinafter referred to as sample gas S) flows. The downstream side of the flow path 6 branches into two flow paths 7 and 8; Filters 9 and 10 and electromagnetic valves 11 and 12 for collecting PM contained in the sample gas S are provided in the respective flow paths 7 and 8, and a sample for flowing the exhaust gas in a steady state through one of the flow paths 7. The gas flow path and the other flow path 8 are each configured as a bypass flow path for flowing an unsteady exhaust gas.
[0005]
Reference numeral 13 denotes a three-way solenoid valve as a flow path switching means provided on the downstream side of the sample gas flow path 7 and the bypass flow path 8. The port 13a is connected to the sample gas flow path 7 and the port 13b is connected to the bypass flow path 8. While being connected, the port 13 c is connected to the gas flow path 14 on the downstream side of the three-way solenoid valve 13.
[0006]
The gas flow path 14 is provided with a suction pump (for example, a roots blower pump) 15 capable of changing the suction capacity by controlling the number of rotations, and a flow meter (for example, a venturi meter) 16 with high measurement accuracy in this order. Reference numeral 17 denotes a pressure sensor for detecting the pressure of the gas flowing through the gas flow path 14, reference numeral 18 denotes a differential pressure sensor, and reference numeral 19 denotes a temperature sensor.
[0007]
Reference numeral 20 denotes an inverter (frequency converter) for controlling the suction pump 15, and 21 denotes a PID controller, which outputs a command to the inverter 20. The constants (P, I, D) in the PID controller 21 are set according to the gas flow rate and the capacity of the suction pump 15. An interface unit 22 receives outputs from the sensors 17 to 19 and commands from the microcomputer 23 to be described later, and can perform some calculations such as a flow rate calculation and outputs commands to the PID controller 21. Is. Reference numeral 23 denotes a microcomputer as an arithmetic control unit that controls the entire apparatus.
[0008]
FIG. 5 schematically shows a control system of the suction pump 15 in the dilution gas flow control device. In this figure, E _INV is a voltage to the inverter 20, E _FF is a feedforward voltage, and E _PID is PID control. The voltage, Q _act is the actual flow rate (actual flow rate) of the gas in the flow path 14, Q _tgt is the target flow rate, R is an integrated reset signal output from the interface unit 22 to the PID controller 21, It is formed based on the flow path switching signal. T, P, dP are detection outputs from the sensors 17-19.
[0009]
In the dilution gas flow control device configured as described above, the command value output by the PID controller 21 is output to the inverter 20, and the roots blower pump 15 is based on the command value output from the inverter 20 based on this command. Is controlled so that the flow rate of the sample gas flowing through the gas flow paths 6 and 14 is always constant. In this case, the flow rate of the sample gas S in the filter 9 (or 10) needs to be always constant. Conventionally, as shown in FIG. The initial pressure setting lines 24 and 25 were connected immediately before the three-way solenoid valve 13, respectively.
[0010]
That is, the initial pressure setting lines 24 and 25 have the same configuration, and include air suction filters 24F and 25F, pressure loss setting needle valves 24N and 25N, and three-way via two-way solenoid valves 24V and 25V. It is connected to the sample gas flow path 7 and the bypass flow path 8 immediately upstream of the electromagnetic valve 13, and is configured to take in air through the filters 24F and 25F. The opening of the needle valves 24N and 25N is manually adjusted to cause initial pressure loss of the filters 9 and 10 provided in the sample gas flow path 7 and the bypass flow path 8, respectively.
[0011]
[Problems to be solved by the invention]
However, in the conventional dilution gas flow control device, the initial pressure setting lines 24 and 25 including the filters 24F and 25F and the needle valves 24N and 25N for setting the pressure loss are provided, and the needle valves 24N and 25N are manually opened. Since the initial pressure setting is performed by adjusting, there are inconveniences that the overall configuration of the device is complicated and time-consuming. In addition, when filters with different initial pressure losses are used, the initial pressure is set by the type of the filter. There is a problem that the flow configuration becomes complicated as much as the lines 24 and 25 need to be provided.
[0012]
On the other hand, it may be possible to automate the setting of the initial pressure loss by driving the needle valves 24N and 25N with a motor. The point that it is necessary to provide it remains as a problem.
[0013]
The present invention has been made in consideration of the above-described matters, and the purpose thereof is a dilution that can automatically set an initial pressure without providing an initial pressure setting line equipped with a needle valve or the like. A gas flow control device is provided.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has filters for collecting PM contained in sample gas branched from a tunnel for diluting sample gas discharged from an engine , and is connected in parallel to each other. A plurality of branch channels, channel switching means for switching the branch channels so that the sample gas flows in one of these branch channels, and a control value from the PI controller or PID controller, To set an initial pressure loss in the filter in a dilution gas flow control device used for a PM measuring device in exhaust gas, which includes a suction pump whose rotation speed is controlled so that the sample gas has a constant flow rate, and a flow meter. to, first, set the filter to operate the suction pump, signal and before SL output to the suction pump of this time The flow rate through the filter as measured by the amount meter, stored in the computer, the signal which is output to the stored the suction pump, from the data of the flow rate through the filter, the signal output to the suction pump, filter Determination of relationship between a passing flow rate, obtains a signal corresponding to the set flow rate when turning on the suction pump by using the relational expression which is set as the initial pressure loss, gives the signal to the PI controller or PID controller by so as to control the suction pump.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. 1 to 3 show one embodiment of the present invention. First, FIG. 1 schematically shows the overall configuration of the dilution gas flow control device of the present invention. In this figure, the same reference numerals as those in FIG. 4 denote the same members. In FIG. 1, reference numeral 26 denotes a three-way electromagnetic valve as a flow path switching means provided on the downstream side of the sample gas flow path 7 and the bypass flow path 8. The port 26a is the sample gas flow path 7 and the port 26b is the bypass flow path. 8 and the port 26 c are connected to the gas flow path 14. Reference numeral 27 denotes a standby line connected between the three-way electromagnetic valve 26 and the suction pump 15 in the gas flow path 14, which includes a two-way electromagnetic valve 28 and a filter 29 so as to take in air through the filter 29. It is configured.
[0016]
Next, the operation of the dilution gas flow control device having the above configuration will be described. The initial pressure loss is set based on the following facts. That is, in general, the flow rate through the filter and the pressure loss in the filter are in a proportional relationship. FIG. 3 shows data indicating this, and a fluid velocity (cm / sec) and a pressure loss (mmH ₂ O) when a fluid (for example, air) is passed using a filter having an outer diameter of 47 mm (effective diameter of 35 mm). ). The numbers shown in the margins on the horizontal axis indicate the fluid flow rate per minute when the outer diameter is 47 mm and the outer diameter is 70 mm (effective diameter 60 mm).
[0017]
For example, in order to set the initial pressure loss of the filter using the sample gas flow path 7, the following sequence may be used.
[0018]
(1) First, a new filter is set in the filter holder.
[0019]
(2) The electromagnetic valve 26 is operated so that the sample gas flow path 7 and the gas flow path 14 are in communication. Then, a signal is output from the inverter 20 to operate the suction pump 15, and air is caused to flow through the gas flow path 14. The flow rate at this time is measured by the flow meter 16. Then, the minimum flow rate Q _min and the maximum flow rate Q _{max are set,} and the minimum voltage value V _min and the maximum voltage value V _max given to the inverter 20 at that time are stored in the microcomputer 23.
[0020]
(3) From the two sets of data obtained in (2) above, that is, the flow rate and voltage data (Q _min , V _min ) and (Q _max , V _max ), the relationship between the flow rate and the voltage is a linear expression Represented by
[0021]
In this case, when the filter types (outer diameter size, effective diameter, etc.) are the same, the formula obtained in (3) above can be applied to all filters, and when the filter types are different. For each of the different filters, the relational expression (primary expression) between the flow rate and the voltage may be obtained by executing the procedures (1) to (3).
[0022]
FIG. 2 shows an example of a screen in the microcomputer 23 when setting the initial pressure loss of the filter. In this example, the case where the types of filters are different is shown.
[0023]
As described above, in the dilution gas flow rate control device of the present invention, the initial pressure loss of the filter can be set by the procedures (1) to (3), but the set flow rate is set when the suction pump 15 is turned on. The corresponding feedforward value (voltage) is obtained from the above linear expression, and this voltage value is given to the PID controller 21, whereby the output given from the PID controller 21 to the inverter 20 starts from the voltage value. Therefore, the delay time is reduced as compared with the case where no feedforward value is given.
[0024]
In the above procedure, when the suction pump 15 is operated to allow predetermined air to flow through the gas flow path 14, the electromagnetic valve 28 is opened to connect the standby flow path 27 to the gas flow path 14. When the air from the standby flow path 27 flows into the gas flow path 14 and the flow rate in the gas flow path 14 is stabilized, the electromagnetic valve 28 is closed, and the electromagnetic valve 26 is operated so that the sample gas flow The path 7 and the gas flow path 14 may be communicated with each other. In this case, the flow rate flowing through the sample gas flow path 7 can be controlled more quickly.
[0025]
In the dilution gas flow control device, when collecting PM, the control is performed as follows. In the steady state, the open / close state of the three-way solenoid valve 26 is set so that the sample gas S flows through the sample gas flow path 7. In this state, the target flow rate Q _tgt and the actual flow rate Q _act are obtained from the interface unit 22. When given to the PID controller 21, the output E _PID is output from the PID controller 21 to the inverter 20 as a command value E _INV based on these differences. The inverter 20 that has received this command value E _INV outputs a command to the suction pump 15. As a result, the suction pump 15 operates at a predetermined rotational speed, and the flow rate of the sample gas flowing through the flow paths 7 and 14 is always controlled to be constant.
[0026]
When the flow path is switched from the above state and the sample gas S is allowed to flow through the bypass flow path 8, first, the command value E _INV to the inverter 20 corresponding to the pressure loss before the flow path switching is stored. .
[0027]
Next, an integrated reset signal R based on the flow path switching signal is input from the interface unit 22 to the PID controller 21 simultaneously with the flow path switching signal or slightly later than this. As a result, the output E _PID from the PID controller 21 to the inverter 20 disappears. At the same time, the stored command value E _INV is _supplied to the inverter 20 as the feed forward signal E _FF without passing through the PID controller 21.
[0028]
As described above, in the dilution gas flow control device according to the present invention, the initial pressure setting sequence can be automatically performed, so that the number of steps for setting the initial pressure can be reduced as compared with the prior art. Unlike the conventional case, since it is not necessary to provide an initial pressure setting line including a needle valve, the configuration of the gas line is simplified, the overall configuration of the apparatus is simplified, and the miniaturization is promoted. Further, it is not necessary to reset the initial pressure every time the flow rate changes.
[0029]
In the above-described embodiment, the PID controller 21 is used, but a PI controller may be used instead.
[0030]
【The invention's effect】
In the dilution gas flow control device of the present invention, the initial pressure can be automatically set without providing an initial pressure setting line equipped with a needle valve or the like, and the entire device is inexpensive and compact. .
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of the configuration of a dilution gas flow control device according to the present invention.
FIG. 2 is a diagram showing an example of a screen in a microcomputer when setting an initial pressure loss of a filter in the apparatus.
FIG. 3 is a diagram illustrating a relationship between fluid velocity and pressure loss in a filter.
FIG. 4 is a diagram schematically showing a configuration of a conventional dilution gas flow control device.
FIG. 5 is a diagram schematically showing a control system of a suction pump in the dilution gas flow control device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Dilution tunnel, 7, 8 ... Branch flow path, 9, 10 ... Filter, 15 ... Suction pump, 16 ... Flowmeter, 20 ... Inverter, 21 ... PID controller, 26 ... Flow path switching means.

Claims (1)

A plurality of branch passages each having a filter for collecting PM contained in the sample gas branched and collected from the tunnel for diluting the sample gas discharged from the engine and connected in parallel to each other, and these branches The sample gas is rotated so that the flow rate of the sample gas becomes constant by the flow channel switching means for switching the branch flow channel so that the sample gas flows in one of the flow channels and the control value from the PI controller or PID controller. In a dilution gas flow control device used in a PM measuring device for exhaust gas having a number-controlled suction pump and a flow meter, in order to set an initial pressure loss in the filter, a filter is first set and the suction pump is operated, the filter measured by said signal output to the suction pump and before Symbol flowmeter at this time Over flow, stored in the computer, obtains a signal output the stored the suction pump, from the data of the flow rate through the filter, the signal output to the suction pump, the relationship between the flow rate through the filter When the suction pump is turned on using the relational expression set as the initial pressure loss, a signal corresponding to a set flow rate is obtained, and this signal is given to the PI controller or PID controller to control the suction pump. A dilution gas flow rate control apparatus characterized by being configured as described above.

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